Turbine rotor



W. K. BODGER TURBINE ROTOR Aug. 16, 1949;

Filed March 27, 1945 FIG.2

INVENTOR Wm Mfl 55 FIG.I v

FIG.3

Patented Aug. 16, 1949 Walter Kenneth Bodger,

assignor to United Aircraft Corpora- Conn.,

South Glastonbury,

tion, East Hartford, Conn, a corporation of Delaware Application March27, 1945, Serial 310,525,162

1 Claim. (01. 253-") This invention relates to turbine rotors andparticularly to rotor disks for gas turbines in which the blade is aceramic material.

The operating temperatures of turbines are limited by the materialsavailable which for the most part rapidly lose strength at the hightemperatures desirable for emcient operation. The metals commonly usedare also subject to creep at high temperatures and may grow, duringoperation at elevated temperatures, to such a dimension that furthersatisfactory operation is impossible. A feature of this invention is aturbine rotor the surfaces of which are of ceramic material.

The rotational speed of the rotor is limited by the permissible stressin the blades. If the blade can be kept at a suillciently lowtemperature the strength of the blade may be kept high enough towithstand the centrifugal stresses resulting from high speeds. A featureof the invention is an arrangement for cooling the structural part ofthe turbine blades.

Since many ceramics do not have a high tensile strength they are notentirely satisfactory in turbine blades because of the high tensilestresses resulting from the centrifugal loads. A feature of thisinvention is a turbine rotor so arranged that the ceramic turbine blademay be compressively loaded. Another feature is the positioning ofthehollow ceramic blade over posts on the rotor in such a manner thatthe ceramic blades are supported by the post and the loading on theblades is compressive. Another feature is the circulation of a coolantthrough the post.

One feature is the supplying of the coolant from the center of the rotorthrough the posts and the discharge of the coolant at the periphery ofthe rotor,

A feature of the invention is the arrangement of the posts so that thecross sectional area decreases toward the periphery of the rotor inorder to reduce the stresses in the post, and the ceramic blade has itscross sectional area increasing toward the periphery of the rotor inorder to reduce the stresses in the blade.

Other objects and advantages will be apparent from the specification andclaim, and from the accompanying drawings which illustrate an embodimentof the invention.

Fig. 1 is a sectional view through the rotor Fig. 2 is an enlargedsectional view showing the manner of mounting the turbine blade.

Fig. 3 is a fragmentary elevation of the periphery of the disk.

Fig. 4 is a transverse sectional view through one form of blade.

The turbine disk may be used in a single stage turbine or may form onestage of a multi-stage turbine of the type shown in the copendingappiication of Bodger, Serial No. 550,872, filed August 23, 1944,although its use is not limited to this particular type of turbine.

As shown, the rotor includes a disk section ll having a number ofradially extending posts or pegs l2 projecting from its outer edge andpreferably structurally integral with the disk. ,Each post preferablytapers toward the outer end in order that the tensile stress developedin this post during the rotation of the disk may be approximatelyuniform throughout the length of the post.

Fitting over the post II, which may be circular in cross section, is aceramic blade it having a similarly shaped central opening. This bladehas its cross-sectional area increasing toward the periphery of therotor in order that the stress may be approximately uniform throughoutthe blade. Mounted at the outer end of east post and connected to thepost as by welding it is a shroud segment it which engages a shoulder 20on the ceramic blade to hold the latter in place on the post. In thismanner, the shroud segment supports the blade at its outer end and theblade is thus loaded in compression when the disk is rotating.

In order that the rotor may operate at high temperatures withoutoverheating, coolant, preferably in the form of relatively cold air, issup-- plied to the central opening 22 in the disk, and passes throughradially extending ducts 24 in the disk and'in each of the posts i2.With coolant flowing through ducts 24 the posts are kept at a relativelylow temperature so that the posts will not be overstressed during theturbine rotation. It will be apparent that the ceramic blade shields thepost from direct contact with the hot fluid that drives the turbine. Theducts 24 are open at their outer ends and the coolant is allowed todischarge from the rotor at this point.

Coolant may be delivered to the central opening 22 of the disk by anydesired mechanism such as that shown, for example, in the Bodgerapplication, Serial No. 550,872, above referred to.

The blade may be held in the desired position with respect to theturbine rotor by the shroud segments it which engage with flanges 28 onthe ceramic blades, as shown in Fig. 3. Each the shroud segments onadjacent posts.

I! desired, the post may be other than circular in cross section, asshown, for example, in Fig. 4 in which the post 28 corresponding to thepost I! of Figs. 1 and 8 is approximately oval shaped in cross sectionto fit a correspondingly shaped opening II in the ceramic blade 82.

It is to be understood that the invention is not limited to the specificembodiment herein illustrated and described, but may be used in otherways without departure from its spirit as defined by the followingclaim.

I claim:

A turbine rotor having a row of blades on its periphery, each bladeincluding a central post integral with the rotor, and a ceramic bladeelement mounted on said post, and a shroud segment on the outer end ofthe post having substantially circumferentially extending side surfaces,said blade element having radially extendirig flanges at the outer endthereof engaging with the Side surfaces of the shroud segment to preventturning of the blade element onthe post.

WALTER-KENNETH BODGER.

REFERENCES CITED The followins references are of record in the file ofthis patent:

5 UNI'I'ED BTATES PATEN'IS Number Name Date 649,014 Terry May 8, 19101,266,889 Wait May 21, 1918 1,362,858 Darling Dec. 21, 1920 1,864,448Lorenzen June 21,1932 1,966,104 Noack July 10, 1934 2,010,022 HolzworthAug. 6, 1935 2,141,401 Martinka Dec. 27, 1938 2,297,508 Schutte Sept.29, 1942 15 2,304,259 Karrer Dec. 8, 1942 2,308,233 Schutte Jan. 12,v1943 2,341,664 Bchutte Feb. 15, 1944 FOREIGN PATENTS 20 Number CountryDate 390,391 Italy May 11, 1940 383,508 Germany Oct. 13, 1923 384,301Great Britain Feb. 2'7, 1931 512,301 Great Britain Aug. 31, 1939 711,421France 1 Sept. 9, 1931

